The present invention relates generally to accessory equipment for oilfield tubular strings, especially casing strings used in casing earth boreholes drilled for oil and natural gas production. More specifically, the present invention relates to casing accessory equipment, including casing string centralizers and "float" equipment used in cementing the casing strings in place, which have bow spring centralizers mounted thereon such that the centralizers may collapse and permit the accessory equipment to readily pass through tight annular clearances (such as through wellheads and the like) no larger than the largest body diameter of the accessory equipment, then permit the centralizers to spring back out to properly centralize the casing string in open hole or a larger casing string.